1. Field of the Invention
The present invention relates to a pneumatic percussion mechanism for a hand-held power tool such as, e.g., a chisel or combination hammer and including a guide tube, an anvil, a percussion piston displaceable in the guide tube for applying impacts to the anvil, a driving member reciprocating in the guide tube for driving the percussion piston and an air spring for transmitting a driving torque from the driving member to the percussion piston and switchable between active and passive conditions.
2. Description of the Prior Art
German Publication DE 43 10 835 A1 discloses a hand-held, electrically driven rotary-percussion or percussion hammer having a motor-driven percussion mechanism arranged in the tool housing. The percussion mechanism includes a driving member, such as a driving piston displaceable in a guide tube and reciprocated with a rod actuatable by the motor. The driving member drives, via an air cushion or an air spring a percussion piston likewise displaceable in the guide tube and applying, through an anvil, blows or impacts to a working tool received in the power tool chuck. The anvil is formed, at its end remote from the working tool, with a pot-shaped section, in the pot space of which the percussion piston is partially received. A seal, which is provided between the pot-shaped anvil and the guide tube seals the percussion mechanism against release of the lubricant outwardly. The air spring is controlled by a sleeve displaceable over the guide tube and which opens or closes aeration bores in the guide tube. The sleeve is controlled indirectly by the anvil. The drawback of the above-described percussion mechanism consists in that several components are needed for controlling the air spring. Therefore, the costs associated with manufacturing and assembly of the percussion mechanism are elevated.
Accordingly, an object of the present invention is to provide a percussion mechanism in which the foregoing drawback of the known mechanism is eliminated, and in which the air spring can be controlled in a simple way.
Another object of the present invention is a hand-held power tool with a percussion mechanism having a simply controlled air spring.